This invention relates generally to steering wheel assemblies and, more particularly, to an integrated steering wheel assembly and a method of manufacturing the integrated steering wheel assembly.
Airbags are located beneath a cover of a steering wheel assembly. Historically, the steering wheel was attached to the vehicle, and the airbag was then attached. A cover was then snapped over the airbag.
More recently, integrated steering wheel assemblies have been proposed wherein the steering wheel and airbag are attached to the vehicle as a modular unit. An integrated steering wheel assembly includes a cover, a steering wheel armature, and an airbag. Most covers are formed of a synthetic plastic material that is molded over a portion of the steering wheel armature and the airbag. The airbag is generally installed after the cover has been molded onto the steering wheel armature and may be installed by a manufacturer other than the manufacturer of the steering wheel armature. Thus, it is generally required that the molding process for the cover provide a cavity between the cover and a portion of the steering wheel armature to accommodate installation of the airbag.
Currently, there are two general methods used to provide the cavity for the airbag. The first method is to use a steering wheel assembly that has a two-piece steering wheel armature. In such a system, the cover is molded over the first piece of the armature. Then, the second piece of the armature is secured to the first piece of the armature and a cavity for the airbag is formed between the two pieces of the armature. The second method is to provide a steering wheel armature that includes a support ring. When the cover is molded over such an armature, the support ring supports the cover and creates a cavity for the airbag. Both methods require a lifter mechanism in the cover mold.
Both of these methods have several disadvantages. First, both require a large amount of material to form either the two-piece armature or the armature and hoop. Material cost can be significant because these parts are often formed from magnesium. Second, both methods require that the steering wheel assembly be relatively thick to accommodate the airbag module. Third, adaptability of these methods to changes in the styling of the cover is very low. Generally, changes in the styling of the cover will require modification of the armature tooling, which causes delays and can be expensive. Fourth, both of these methods frequently suffer from the defect of the lifter mechanism in the cover mold producing a read-through line in the cover material. Finally, with the prior methods, it has proven difficult to control the thickness of the cover forwardly of the airbag.
Thus, it is desirable to produce a method and design for an integrated steering wheel assembly that is simpler and that eliminates the additional elements of either a two-piece armature or an armature with a hoop. Such a design would enable a reduction in cost of the integrated steering wheel assembly. It is also desirable to produce an integrated steering wheel assembly that is readily adaptable to changes in styling of the cover without requiring a change in the tooling for the armature. It is furthermore desirable to eliminate read-through lines in the cover material and to simplify the cover mold.
This invention provides a method and an assembly that has a one-piece armature design that is readily adaptable to changes in styling of the cover and that can be produced in a simplified mold without any read-through lines.